1. Field of the Invention
The present invention relates to an analyzer which analyzes a chromatogram obtained by applying a sample containing an analyte to liquid chromatography or gas chromatography using a column or the like.
2. Discussion of Background
In qualitative and quantitative analyses of analytes, for example, by liquid chromatography, chromatograms obtained are analyzed by detecting analyte peaks and determining their heights, widths and areas.
Chromatograms are analyzed by detecting peaks emerging during elution of analytes and then matching of the detected peaks with expected components (hereinafter referred to as the first method), or by seeking peaks around predicted peak emergence times (reference peak emergence times) for respective analytes of interest (hereinafter referred to as the second method).
In the first method, peaks attributable to unexpected unknown components as well as peaks attributable to expected components are detected, and peaks are defined as the highest points between the initial points and terminal points of the peaks defined on the basis of the slope of the chromatogram. However, noises which are not attributable to any components in the sample are likely to be detected as peaks. Also, there is a problem that the initial points and terminal points of peaks can not be detected correctly with drifting baselines (unstable baselines) because the slope of the chromatogram can not be sensed correctly.
In contrast, the second method has an advantage that peaks attributable to expected analytes can be detected correctly, though other peaks are not detected by the second method.
Still, for correct analyses of chromatograms, proper baseline establishment is needed in addition to correct detection of analyte peaks.
In conventional peak analyses, a baseline is defined as the straight line joining first and second baseline points provided on the chromatogram before and after the emergence time of a detected analyte peak with a certain time gap, for example, corresponding to a multiple of the peak width at half the peak height (the half width).
Therefore, if a baseline point determination of the baseline of an analyte falls inside a peak attributable to another component or a ghost peak (resulting from, for example, a switching valve operation for sample injection in liquid chromatography), the level of the chromatogram at the baseline point shifts from the level of the true baseline, and consequently, for example, in a peak analysis based on peak height, the peak height obtained as the result of the analysis is different from the true value. Because peaks attributable to components other than analytes and ghost peaks emerge at different times in different sizes depending on not only the kinds of the components and analysis conditions but also analysis environments such as room temperature, there is a problem that it is necessary to determine new baseline points which do not fall inside these peaks every time the analysis environments change in order to give a proper baseline.
Accordingly, the object of the present invention is to provide a chromatogram analyzer for use after peak detection, for example, based on predicted peak emergence times (reference peak emergence times) for respective analytes of interest, which can determines proper baselines even in the presence of peaks attributable to components other than the analytes or ghost peaks.
In order to achieve the above-mentioned object, according to claim 1 of the present application (hereinafter referred to as the first aspect of the present invention), the present invention provides a chromatogram analyzer which analyzes a chromatogram obtained by applying a sample containing an analyte, which comprises a first storage means which stores a baseline detection starting time (tb1) and a baseline detection ending time (tb2) (wherein tb1 less than tb2) for determination of a baseline used for analysis of an analyte peak; a second storage means which stores a chromatogram of the analyte; a first arithmetic means which detects an analyte peak and its emergence time (tx, wherein tb1 less than tx less than tb2) on the chromatogram; and a second arithmetic means which detects a first baseline point between tb1 and tx by using a function having at least one of the level, the slope, the curvature and the gap from tx of the chromatogram at a particular point as the variables, detects a second baseline point between tx and tb2 by using a function having at least one of the level, the slope, the curvature and the gap from tx of the chromatogram at a particular point as the variables and gives a straight line passing through the first baseline point and the second baseline point as the baseline.
According to claim 2 of the present application (hereinafter referred to as the second aspect of the present invention), the present invention also provides a chromatogram analyzer which analyzes a chromatogram obtained by applying a sample containing an analyte, which comprises a first storage means which stores a baseline detection starting time (tb1) and a baseline detection ending time (tb2) (wherein tb1 less than tb2) for determination of a baseline used for analysis of an analyte peak; a second storage means which stores a chromatogram of the analyte; a first arithmetic means which detects an analyte peak and its emergence time (tx, wherein tb1 less than tx less than tb2) on the chromatogram; and a second arithmetic means which detects a first baseline point between tb1 and tx by using a function having at least one of the level, the slope, the curvature and the gap from tx of the chromatogram at a particular point as the variables, defines the point on the chromatogram at tb2 as a second baseline point and gives a straight line passing through the first baseline point and the second baseline point as the baseline.
According to claim 3 of the present application (hereinafter referred to as the third aspect of the present invention), the present invention further provides a chromatogram analyzer which analyzes a chromatogram obtained by applying a sample containing an analyte, which comprises a first storage means which stores a baseline detection starting time (tb1) and a baseline detection ending time (tb2) (wherein tb1 less than tb2) for determination of a baselines used for analysis of an analyte peak; a second storage means which stores a chromatogram of the analyte; a first arithmetic means which detects an analyte peak and its emergence time (tx, wherein tb1 less than tx less than tb2) on the chromatogram; and a second arithmetic means which defines the point on the chromatogram at tb1 as a first baseline point, detects a second baseline point between tx and tb2 by using a function having at least one of the level, the slope, the curvature and the gap from tx of the chromatogram at a particular as the variables and gives a straight line passing through the first baseline point and the second baseline point as the baseline.
According to claim 4 of the present application (hereinafter referred to as the fourth aspect of the present invention), the present invention further provides a chromatogram analyzer which analyzes a chromatogram obtained by applying a sample containing an analyte, which comprises a first storage means which stores a baseline detection starting time (tb1) for determination of a baseline used for analysis of an analyte peak; a second storage means which stores a chromatogram of the analyte; a first arithmetic means which detects an analyte peak and its emergence time (tx, wherein tb1 less than tx) on the chromatogram; and a second arithmetic means which detects a baseline point between tb1 and tx by using a function having at least one of the level, the slope, the curvature and the gap from tx of the chromatogram at a particular point as the variables and gives a straight line parallel to the time axis and passing through the baseline point as the baseline.
According to claim 5 of the present application (hereinafter referred to as the fifth aspect of the present invention), the present invention further provides a chromatogram analyzer which analyzes a chromatogram obtained by applying a sample containing an analyte, which comprises a first storage means which stores a baseline detection ending time (tb2) for determination of a baseline used for analysis of an analyte peak; a second storage means which stores a chromatogram of the analyte; a first arithmetic means which detects an analyte peak and its emergence time (tx, wherein tx less than tb2) on the chromatogram; and a second arithmetic means which detects a baseline point between tx and tb2 by using a function having at least one of the level, the slope, the curvature and the gap from tx of the chromatogram at a particular point as the variables and gives a straight line parallel to the time axis and passing through the baseline point as the baseline.